There are many suture anchor designs on the market today which are intended to secure suture, wherein the suture is passed through soft tissue to bone. Preferred methods often use anchors that do not require placing knots in the suture to secure the tissue to the anchor. This shift has allowed for a simpler, less time consuming procedure. Also, the knots have been shown to be a common source of anchor failure.
However, the knotless anchors have many challenges. Many anchors can change the tension in the suture during deployment, which requires the surgeon to estimate how much tension will be added during the final installation step. This can result in under- or over-tensioning of the tissue against the bone. Anchors that allow the suture to be tensioned after the anchor is implanted can be complicated, with many components which lead to expensive and unreliable anchors. These types of anchors can have user-assisted tensioning devices that can lead to over-tensioned suture that have the ability to pull the anchor out of the bone.
Other anchors that allow the suture to be tensioned prior to implanting the anchor can leave the sutures with uneven tension. Also, many of the anchors are unable to utilize more than two suture ends and have undesirable metal components.
There have been many different anchors used t secure suture to bone. As described above, the knotless anchor designs are preferred due to knot failures.
The PUSHLOCK™ anchor, marketed by Arthrex, is a two-part anchor. The tip of the anchor has an eyelet through which the suture legs are loaded. This tip is placed at the bottom of a hole drilled into the bone. At this point, the surgeon may adjust the tension on the suture, thereby pulling the tissue closer to the surface of the bone. Since the suture is tensioned all at once, without any engagement with the hole when the rear portion of the anchor is driven into the hole, the tension may not be correct. Once the rear portion of the anchor is in the hole, the suture tension cannot be adjusted.
Smith and Nephew market the KINSA™ suture anchor. This anchor is a knotless design made of PEEK (polyether ether ketone) which is tapped into a pre-drilled hole in the bone. The anchor is preloaded with suture tied in a one-way sliding knot within the anchor body, which allows the surgeon to adjust the tension after the anchor has been deployed. This cannot utilize suture that is already passed through tissue and only can provide a simple stitch in the tissue.
The POPLOK™ by Conmed Linvatec is another knotless anchor. It is a two piece polymer anchor that has the ability of accepting and tensioning the suture individually prior to locking the suture to the anchor. However, the anchor has multiple pieces that can fail.
The VERSALOK™ by Mitek is also a knotless anchor. It is a two piece polymer and metal design that has the ability of accepting and tensioning the suture individually prior to locking the suture to the anchor. It does have multiple parts forming the anchor and the inner member is metallic.
The CUFFLINK™ Knotless and CUFFLINK SP™ Knotless suture (self punching with metal tip) anchors, also marketed by Mitek, are fabricated of PEEK, using a one-piece polymer design without the employment of any metal. The design allows the anchor to accept more than two suture ends, and each of these ends can be tensioned or have tension released individually by hand, prior to final anchor deployment, providing the surgeon the ability to achieve the desired tension on each suture. The anchor may also accept tissue (such as a tendon, ligament, zenograft, allograft, or collagen scaffold) with or without suture, enabling a direct tissue to bone repair. The metal tip version allows the anchor to be malleted directly into the bone without the need for a pilot hole. Finally, the design incorporates a metal deployment device to provide strength to the anchor during deployment, thereby reducing breaking of the anchor.